Answer
a. 49.31%
b. 78.92 amu
Work Step by Step
a) Abundance I2= 100% - abundance I1 = 100% -50.69% = 49.31%
b) Atomic mass = (mass I1)(Abundance I1)+(mass I2)(abundance I2)
So, mass I1 = \frac{Atomic mass - (mass I2)(Abundance I2)}{Abundance I1}
=\frac{79.904 - (80.9163)(0.4931)}{50.69%}
=78.92 amu
